control logic

Soft

start

Thermal

Shtdwn

UVLO

PG control

power

control

error

amplifier

gate

drive

HS lim

LS lim

PVIN

PVIN

AVIN

PG

PGND

PGND

AGND

comp

comp

+

_

DCS - Control

TM

direct control

&

compensation

comparator

ramp

SW

SW

SW

EN

*

SS/TR

DEF

*

FSW

*

VOS

FB

*

(see Detailed Description section).

TPS62140, TPS62140A

TPS62141, TPS62142, TPS62143

SLVSAJ0C – NOVEMBER 2011 – REVISED AUGUST 2015

www.ti.com

Functional Block Diagrams (continued)

Figure 6. TPS62141/2/3 (Fixed Output Voltage)

8.3 Feature Description

8.3.1 Enable / Shutdown (EN)

When the enable pin (EN) is set High, the device starts operation.

Shutdown is forced if EN is pulled Low with a shutdown current of typically 1.5 µA. During shutdown, the internal

power MOSFETs as well as the entire control circuitry are turned off. The internal resistive divider pulls down the

output voltage smoothly. An internal pulldown resistor of about 400 k

Ω is connected and keeps EN logic Low if

the pin is floating. It is disconnected if the pin is High.

Connecting the EN pin to an appropriate output signal of another power rail provides sequencing of multiple

power rails.

8.3.2 Soft-Start / Tracking (SS/TR)

The internal soft-start circuitry controls the output voltage slope during start-up. This avoids excessive inrush

current and ensures a controlled output-voltage rise time. It also prevents unwanted voltage drops from high-

impedance power sources or batteries. When EN is set to start device operation, the device starts switching after

a delay of about 50 µs, and VOUT rises with a slope controlled by an external capacitor connected to the SS/TR

pin. See Figure 34 and Figure 35 for typical start-up operation.

8

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